1. Field of the Invention
This invention relates generally to size reduction apparatus, and in particular to a rotary shear for particulating paper.
2. Description of the Prior Art
Rotary shears are known for granulating, shredding, particulating or otherwise reducing the size of diverse materials such as paper, plastic scrap, metal scrap and metal sponge. The purpose of such machines is to reduce the work materials to a predetermined particulate size or fineness. In the disposal of paper materials such as confidential business documents, clasified government documents, and paper currency which has been withdrawn from circulation, it is desirable to reduce the paper materials to a comminuted product having a fine consistency. It will appreciated that high volume disposal operations require a machine which is capable of operating at high RPM levels, and which can reduce a large mass of material quickly and efficiently.
A common problem in the operation of such rotary shear machinery is the maintenance of sharp cutting edges on the rotor and stator blades. Installation and removal of stator blades on most machines is simiplified by the location of the stator blades in accessible locations. The rotor assembly, on the other hand, is relatively inaccessible and must be removed from the stator to provide access to the rotor blades. The rotor assembly removal and installation operations are difficult in most conventional machines because of adjustment of end bearing loading and rotor-stator blade clearance to close tolerances.
Improved rotor assemblies are known in which rotor blades are integrally formed with the rotor shaft. In such rotor assemblies in which the blades are integrally formed either by casting or by machining, it is known to form each rotor blade along a spiral path with respect to the rotor axis. Such rotor assemblies have achieved only limited commercial success because of the fabrication expense and because of the difficulty of sharpening the spiral cutting edges of the rotor blades.